1. Field of the Invention
The present invention relates to a differential gear combined with a differential lock mechanism.
2. Description of Background Art
For example, in the two-wheel drive vehicle, since the radii of turn for the respective right and left drive wheels are different, a differential gear for distributing drive torque to the respective wheels while absorbing a difference in the revolution of these wheels, or generating revolutions suitable for the respective wheels is required when the vehicle turns.
Though this differential gear absorbs the difference of revolution, when one of the left and right drive wheels slips on a road surface of low frictional coefficient, a drive force of the other one of those wheels is reduced, and hence the total drive force is lowered. Therefore, especially in the case of four-wheel drive vehicles or special vehicles for rough terrain drive is provided with Limited-Slip Differentials for limiting the differential of motion between the respective wheels to secure a driving force between the left and right drive wheels.
A final reduction gear provided with such a Limited-Slip Differential in the related art will be described below (See, also JP-A-071773/2001).
FIG. 12 is a cross-sectional view of a final reduction gear in the related art. The final reduction gear 200 includes a differential case 204 constructed by coupling a drive pinion 202 to the engine via a joint 201, meshing a ring gear 203 with the drive pinion 202, and mounting a cap 203a on the ring gear 203. This device allows for the input-side blocks 205, 206 to engage the inner peripheral surface of the differential case 204, clamping these input-side blocks 205, 206 between two output-side cams 207, 208, coupling the drive shafts 211, 212 to the output-side cams 207, 208 respectively, and connecting the wheels with the drive shafts 211, 212. A housing 214, 215 is illustrated in FIG. 12.
The differential case 204, the input-side blocks 205, 206 stored in the differential case 204, and the output-side cams 207, 208 described above are main elements that constitute a Limited-Slip Differential 220 adapted to generate friction torque for limiting differential.
Power is transmitted in the following order of engine→the joint 201→the drive pinion 202→the ring gear 203→the differential case 204→the input-side blocks 205, 206→the output-side cams 207, 208→the drive shafts 211, 212→the wheels.
The frictional force generated when slippage occurs independently at the input-side blocks 205, 206, the output-side cam 207, the input-side blocks 205, 206, and the output-side block 208, limits the differential of motion between the left and right wheels.
In the final reduction gear 200 described above, for example, when the left and right wheels drive on road surfaces that are different in frictional coefficient respectively, the Limited-Slip Differential 220 ensures a drive force of the wheel driving on the road surface having higher frictional coefficient. However, especially on a slippery muddy ground surface and the like, a driving force may be transmitted to neither of wheels. Therefore, employment of a function to disable differential between both wheels, or a so-called differential lock, is desired. However, significant modification of the construction of the final reduction gear 200 in the related art results in a significant increase in costs.